EP4106940B1 - Aerostatic bearing for a rotor, in particular in a balancing machine - Google Patents

Description

The invention relates to an aerostatic bearing with a bearing element arranged in a housing in a rotationally fixed manner and a rotor rotating about its axis of rotation.

In machines, the rotation of parts is often made possible by mounting the parts on bearing spindles, whereby a fluid medium is supplied to the rotating machine parts for working processes. Rotary joints that work with contacting seals and bearings can be used for this supply. However, these contacting parts are disadvantageous in balancing technology, as the frictional forces on the seals and processes in the bearings can cause disturbing vibrations. Hydrostatic or aerostatic bearings do not have these disadvantages.

Aerostatic bearings are known in which the two partners moving against each other are separated from each other by a thin film of air. The separating film of air is created by introducing compressed air into the bearing gap. Aerostatic bearings are very suitable for supporting a rotor in a balancing machine, as they ensure that the rotor runs very evenly and with little disruption, thus enabling precise unbalance measurement.
Out of US 3 476 451 A an aerostatic bearing for a shaft is known in which two conical bearing bodies are arranged opposite each other on the shaft and are accommodated in matching bearing elements. The bearing elements are accommodated in housing bores so that they can move axially and radially and are sealed by means of sealing rings that dampen radial vibration movements.

EN 10 2013 108 956 B3 discloses an aerostatic bearing for a rotatable rotor, which has an axis of rotation and a bearing surface extending radially to the axis of rotation, wherein a bearing element is arranged non-rotatably in a bore of a housing. The bearing element has a counter bearing surface that interacts with the bearing surface and at least one supply channel for compressed air that opens into the counter bearing surface and is mounted so that it can move in the direction of the axis of rotation against opposing forces that determine its position in the housing and is in operative engagement with a damping body that is designed to dampen vibrations of the axial movements of the bearing element.

EN 25 22 260 A1 describes a device for balancing machines for clamping and centering axisless rotating bodies that have a vacuum between the balancing holder and the rotating body surface. The support plate has a cone in the middle and inner and outer elastic sealing rings. The rotor is clamped axially against the support plate by a vacuum, with the vacuum supply between the two sealing rings being carried out by the balancing machine spindle.

EN 38 38 303 A1 reveals a rotary union for two different fluids.

Out of US 5 553 948 A A compressed air device is known in which a spindle is guided in a clamping and bearing sleeve. At the head of the spindle there is a table in front of it and a pressure plate opposite the table. A workpiece can be mounted on the table for inspection, which is sucked onto the table via a simple suction mechanism. Plate-shaped bearing elements are arranged above and below the pressure plate so that an axial bearing gap is formed. Air can be introduced into the gap via nozzles. At the same time, the axially extending outer surface of the spindle together with the bearing sleeve forms a radial bearing gap, into which compressed air can also be introduced. The compressed air can escape via lines that are arranged between the clamping sleeve and the bearing sleeve. The arrangement of the lines prevents the compressed air from causing dust turbulence that could contaminate the workpiece being examined. In addition, escaping compressed air can be removed via the suction mechanism.

DE 94 14 006 U1 discloses a hollow spindle with a coupled collet, in which the hollow spindle is aerostatically mounted in a bushing inserted in a housing. The clamping device is actuated by a piston that is supplied with compressed air via a supply line, with the opposite movement of the piston being caused by a compression spring.

The disadvantage of the current state of the art is that there are no solutions for the known bearings that allow the supply and removal of actuating air. The bearings only deal with the supply and removal of the compressed air required for the air bearing.

The invention is based on the object of providing an aerostatic bearing which does not have the disadvantages of the known bearings and which facilitates the actuation of a pneumatic clamping device.

The problem is solved by the teaching of claim 1. Advantageous embodiments are listed in the dependent claims.

The object is achieved according to the invention in that an aerostatic bearing is provided for a rotatable rotor, which has an axis of rotation and an axial bearing surface extending radially to the axis of rotation and a radial bearing surface extending axially to the axis of rotation, with a non-rotatably arranged bearing element in a bore of a housing, which has an axial counter-bearing surface interacting with the axial bearing surface and a radial counter-bearing surface interacting with the radial bearing surface, into each of which at least one supply channel for supplying compressed air opens, wherein the rotor has a central Cavity which is designed to accommodate a pneumatically actuated tool clamping device and the cavity is connected via communicating supply lines penetrating the rotor and the rotationally fixed bearing element to supply and discharge lines formed in the housing for the supply and discharge of actuating air. The bearing according to the invention represents a combination with which not only the Bearing of a rotor is achieved, but also the actuation of a pneumatic clamping device is possible. A compressed air system connected to the aerostatic bearing can thus be used to provide the compressed air required for the bearing and the actuating air required for the pneumatic actuation. No separate solutions are required for the supply and removal of actuating air. With the bearing according to the invention, which is used in particular in balancing machines, the supply and removal of compressed air required for the bearing as well as the supply and removal of actuating air can be ensured.

The use of the aerostatic bearing enables the provision of a narrow bearing gap, which is advantageous not only for the bearing of the rotor, but also for the function of the pneumatically operated tool clamping device. Experience shows that with other bearings, a bearing cannot be achieved that is as precise as with an aerostatic bearing, which in turn results in a larger bearing gap and, due to the leak, is accompanied by an inaccurate function of a pneumatically operated tool clamping device. Regarding the advantages of an aerostatic bearing, reference is made to the EN 10 2013 108 956 B3 reference is made.

The bearing element can be designed as a particularly ring-shaped element. However, it can also be provided that the bearing element is designed in two parts and comprises an upper and a lower bearing sleeve. This means that the bearing element can be integrated into balancing machines of different designs, since it can be easily adapted to the length of the holder. In this regard, it is advantageous if the lower and upper bearing sleeves each have a radial counter-bearing surface into which at least one feed channel opens.

It is particularly advantageous for the bearing if the bearing element has at least two, preferably three in the radial counter bearing surface opening feed channels. If the bearing element is divided into a lower and an upper bearing sleeve according to an advantageous embodiment, it is advantageous that one of the two bearing sleeves has a feed channel and either the upper or the lower bearing sleeve has two feed channels. The upper bearing sleeve and the lower bearing sleeve therefore have at least one radial bearing, each of which forms a radial bearing surface. In one embodiment, only the upper bearing sleeve has an axial bearing, i.e. an axial counter-bearing surface into which a feed channel opens and which interacts with the axial bearing surface of the rotor. However, it can also be provided that the lower bearing sleeve has an axial bearing in addition to or instead of the upper bearing sleeve, which correspondingly forms an axial counter-bearing surface that interacts with an axial bearing surface of the rotor.

Between the rotor and the bearing element, i.e. in particular between the bearing surfaces, there is advantageously a bearing gap into which compressed air can be introduced via the supply channels. Compressed air is introduced into the bearing gap so that the rotor is supported on an air cushion. The air can be discharged using discharge channels and discharge lines in the bearing element or the housing, as well as any annular gaps between the rotor and the bearing element through which the exhaust air can escape.

It is intended that the rotor is designed in the shape of a bush and has an annular flange at its upper end, which extends radially outwards from the bush and forms the axial bearing surface, which interacts with the axial counter-bearing surface of the bearing element. The axial bearing surface is essentially opposite the counter-bearing surface, so that an air cushion can form between the two surfaces.

In order to achieve rotation of the rotor, which can be designed as a spindle body, the rotor can be connected with its lower end in a rotationally fixed manner to a The rotor can be connected to a connection for the rotary drive, for example by means of fastening elements that engage in corresponding holes in the rotor.

In order to ensure that the actuating air flows into the rotor in a controlled manner, valves can be installed upstream of the supply lines for supplying actuating air into the cavities for the purpose of control. This allows the pneumatic clamping device to be easily controlled by regulating the supply of actuating air.

The aerostatic bearing is preferably used in balancing machines. This means that the described designs and advantages also preferably apply to a balancing machine with an aerostatic bearing. The invention therefore also relates to a balancing machine with a previously described aerostatic bearing for a rotatable rotor, which has an axis of rotation and an axial bearing surface extending radially to the axis of rotation and a radial bearing surface extending axially to the axis of rotation, with a non-rotatably arranged in a bore of a housing, which has an axial counter-bearing surface interacting with the axial bearing surface and a radial counter-bearing surface interacting with the radial bearing surface, into each of which at least one supply channel for supplying compressed air opens, wherein the rotor has a central cavity which is designed to accommodate a pneumatically actuated tool clamping device and the cavity is connected via communicating supply lines penetrating the rotor and the non-rotatably bearing element to supply and discharge lines formed in the housing for the supply and discharge of actuating air.

The invention is explained in more detail below using an embodiment of the invention, which is shown in the Figure 1 is shown.

The drawing shows a section of a bearing spindle of a balancing machine with an aerostatic bearing for balancing rapidly rotating tools such as milling cutters, drills, etc. for high-speed machining. The bearing comprises an outer spindle housing in which a bearing element 1 is arranged non-rotatably in a bore in the housing. Adjacent to this is a rotating rotor 2 designed as a spindle body. The spindle body forms a substantially cylindrical receptacle to accommodate a tool to be balanced.

The bearing element 1 is applied to a housing 3 with a cylindrical housing bore and comprises Figure 1 a first upper bearing sleeve 4 and a second lower bearing sleeve 5. The bearing element 1 can, however, also be designed in one piece. The bearing sleeves 4, 5 can each be designed as an annular body or as two separate rings which are axially supported by a support means 6 provided in the housing 3, which can be formed by shoulders or other means present in the housing 3. The upper bearing sleeve 4 forms, with its upper axial end, an axial bearing 7 for a flange 8 of the rotor 2 designed as a spindle body and thus forms an axial counter-bearing surface extending radially to the axis of rotation, which interacts with the axial bearing surface formed by the flange 8 of the rotor 2. The upper bearing sleeve 4 and the lower bearing sleeve 5 each form a radial bearing 9 for the rotor 2 and thus form a radial counter-bearing surface extending axially to the axis of rotation, which interacts with a radial bearing surface of the rotor 2, which is formed by the outer surface of the rotor 2. They are each combined with an annular feed element 24, 25 for supplying the actuating air via the feed line 23. The feed elements 24, 25 and the respective bearing sleeves 4, 5 can be designed as one piece or in multiple parts. This means that a feed element 24, 25 can be designed as a component of a bearing sleeve 4, 5 or alternatively can be reversibly connected to it.

The rotor 2, designed as a spindle body, consists of a substantially cylindrical bushing with the annular flange 8 arranged at the upper end, which extends radially outwards from the bushing. The rotor 2 is supported by the two radial bearings 9 of the bearing element 1 and the axial bearing 7, with a bearing gap 10 between the axial bearing surface or radial bearing surface of the rotor 2 and the radial or axial counter bearing surfaces of the bearing element 1. The rotor 2 can be connected in a rotationally fixed manner to a rotary drive by means of fastening means at its end opposite the flange 8. The rotor 2 has a central cavity 11, which is designed to accommodate a pneumatically actuated tool clamping device 12.

Several, in particular three, supply channels 13 in the form of capillary bores or throttle bores open into the radial bearing surface, extending radially through the bearing element 1, in particular through the upper and lower bearing sleeves 4, 5, which are connected to annular grooves 14 in the housing 3 and guide supplied compressed air into the radial bearings 9. The annular grooves 14 can, for example, be partially supplied with compressed air via axial air channels (not shown) in the housing 3, which can be connected to a connection to a compressed air source for the radial bearings 9. In the bearing element 1, i.e. in the upper and lower bearing sleeves 4, 5, discharge channels are also provided, which open into annular grooves 15 in the housing 3, through which the introduced compressed air can escape.

A supply channel 13 in the form of a capillary bore or throttle bore extends through the bearing element 1 and opens into the axial bearing 7 of the upper bearing sleeve 4, or more precisely the axial counter bearing surface of the bearing sleeve 4. The supply channel can be fed with compressed air from holes (not shown) in the housing 3. The compressed air fed into the axial bearing surface can escape, for example, via an annular gap 16 between the housing 3 and the rotor 2. The compressed air can also escape via other discharge channels 15 in the bearing element 1.

Inside the rotor 2, which is designed as a spindle body, there is a system 12 for clamping the tool to be balanced, or its holder. Such holders are known to the expert, for example, as steep taper systems or hollow shaft taper systems. In the Figure 1 a hollow shaft cone system is shown as an example, but is not limited to this. The clamping system 12 comprises a receptacle 17, which is supported by a circumferential flange on the flange 8 of the rotor 2. The clamping system 12 also comprises a clamping sleeve 18, a clamping bolt 19 and a clamping piston 20, which form a pneumatically actuated tool clamping device 12 with which the tool can be clamped. The clamping piston 20 rests with its disk-shaped piston head, in particular its peripheral surface, on the rotor 2 and divides the cavity 11 of the rotor 2 into essentially two chambers 21, 22, namely an upper 21 and a lower chamber 22. A seal, such as a sealing ring, can rest in the inner circumferential surface of the rotor 2.

In the bearing element 1, feed lines 23 are also provided in the feed elements 24, 25, which open into the cavity 11 formed by the rotor 2. The feed lines 23 mentioned can be supplied with compressed air via supply lines in the form of holes in the housing 3. Compressed air in the form of actuating air can be introduced into the upper chamber 21 via the feed line 23 via the upper bearing sleeve 4, whereas actuating air can be introduced into the lower chamber 22 via feed lines 23 in the lower bearing sleeve 5. It is advantageous if the bearing element 1 has at least one feed line 23, preferably several feed lines 23. If the bearing element 1 is divided into an upper and lower bearing sleeve 4, 5 according to one embodiment, at least one feed line 23 is advantageously present in each of the upper and lower bearing sleeves 4, 5.

In order to achieve an operational state of the bearing, compressed air is simultaneously supplied to the radial bearings 9 and the axial bearing 7 via the connections.

In order to clamp the tool, actuating air is also fed through the supply line and feed line 23 of the upper bearing sleeve 4, which are present in the housing 3 and are designed, for example, as a bore, into the upper chamber 21, so that the clamping piston 20 is moved downwards.

In order to move the clamping piston 20 in the opposite direction and to relax the tool, the supply of actuating air into the upper chamber 21 is interrupted, for example via a valve, whereas actuating air is introduced into the lower chamber 22 via another valve through the supply line and feed line 23 designed as a bore, so that the clamping piston 20 moves upwards. Of course, several feed lines opening into the upper or lower chamber 21, 22 can be provided (not in Figure 1 shown), which are fed with actuating air from corresponding supply lines in the housing and which, depending on the valve setting, can serve as a supply line for supplying actuating air or as discharge lines for pressure relief, i.e. for discharging actuating air. Furthermore, in an embodiment not shown, it can be provided that the actuating air escapes from the upper and lower chambers 21, 22 via separate supply lines that are separate from the supply lines and which have discharge lines in the housing and are designed as bores.

In the invention, the aerostatic bearing and sealing gap system are combined in at least one particularly annular body and an actuation of a pneumatic tool clamping device is possible. The aerostatic bearing guides the rotor very precisely so that the sealing gap for The transmission of compressed air can be carried out very tightly. The amount of air leakage can therefore be considered to be low.

Claims (10)

1. Aerostatic bearing with a rotatable rotor (2) which has an axis of rotation and an axial bearing surface extending radially to the axis of rotation and a radial bearing surface extending axially to the axis of rotation, with a rotationally fixed bearing element (1) which is arranged non-rotatably in a bore of a housing (3) and which has an axial counter-bearing surface cooperating with the axial bearing surface and a radial counter-bearing surface cooperating with the radial bearing surface, into each of which at least one supply channel (13) for supplying compressed air opens, the rotor (2) having a central cavity (11) which is designed to accommodate a pneumatically actuatable tool clamping device (12), and the cavity (11) being connected via communicating supply lines (23), which penetrate the rotor (2) and the rotationally fixed bearing element (1), to supply and discharge lines, which are formed in the housing (3), for the supply and discharge of actuating air.
2. Aerostatic bearing according to claim 1, characterized in that at least two supply channels (13) opening into the radial counter-bearing surface are present.
3. Aerostatic bearing according to one of claims 1 or 2, characterized in that the bearing element (1) is designed in two parts and comprises an upper and a lower bearing sleeve (4, 5).
4. Aerostatic bearing according to claim 3, characterized in that the bearing sleeves (4, 5) each have a radial counter-bearing surface into which at least one supply channel (13) opens.
5. Aerostatic bearing according to one of the preceding claims, characterized in that there is a bearing gap (10) between the rotor (2) and the bearing element (1), into which compressed air can be introduced via the supply channels (13).
6. Aerostatic bearing according to one of the preceding claims, characterized in that the rotor (2) is bush-shaped and at its upper end there is an annular flange (8) which extends radially outwards from the bush and forms the axial bearing surface.
7. Aerostatic bearing according to one of the preceding claims, characterized in that the lower end of the rotor (2) can be connected to a rotary drive in a rotationally fixed manner.
8. Aerostatic bearing according to one of the preceding claims, characterized in that a clamping piston (20) bears with its disc-shaped piston head against the rotor (2) and divides the cavity (11) of the rotor (2) into two chambers (21, 22).
9. Aerostatic bearing according to claim 8, characterized in that valves are connected upstream of the supply lines (23) for the supply of actuating air into the chambers (11, 21) for the purpose of control.
10. Use of the aerostatic bearing according to claims 1 to 9 in a balancing machine.

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